Headlight issue....86 C10

[CamSmoky]

1986 C10 Custom Deluxe Step-side.
The truck is in show condition, everthing is perfect. Just started last time I drove it at night(seldom do) and the headlights will shut off on their own after about 15-20 minutes of being on. 2-3 minutes later they come back on by themselves. I recently rebuilt the alternator and problem is still present. It has me baffled as of now as I am no electrical guru, but know a decent amount about it and have diagnosed issues before. Anyone have any ideas what might be going on? Its almost like something gets hot, then once it cools down it starts working again. All grounds are clean and tight, the headlights are aftermarket with the replacement bulbs, not the whole headlight assembly like stock. Worked great for 7 years I have had the truck finished, just noticed this last time I drove it at night.

Thanks in advance from Kansas...